期刊
ACS APPLIED MATERIALS & INTERFACES
卷 9, 期 33, 页码 27809-27816出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.7b08574
关键词
quantum dot; light-emitting diodes; exciton recombination zone; fluorescent probe; Forster resonant energy transfer; direct charge recombination
资金
- National Natural Science Foundation of China [61405089]
- Guangdong Natural Science Funds for Distinguished Young Scholars [2016A030306017]
- National Key R&D Program of China [2016YFB0401702]
- Guangdong Special Support Program for Young Talent Scholar [2014TQ01X015]
- Shenzhen Peacock Plan [KQTD2015071710313656]
Exciton recombination zone, where the photons are generated, can greatly affect the performance, such as the efficiency and color purity, of the quantum dot (QD) light-emitting diodes (QLEDs). To probe the exciton recombination zone, 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) is doped into the charge transport layer as a fluorescent sensor; by monitoring the Forster resonant energy transfer (FRET) between QD and DCJTB, the location of the recombination zone can be determined. It is found that the electron transport layer (ETL) has a great impact on the recombination zone. For example, in QLEDs with ZnMgO ETL, the recombination zone is near the interface of the QD/hole transport layer (HTL) and is shifted to the interface of the QD/ETL as the driving voltage is increased, whereas in devices with 1,3,5-tris(2-N-phenylbenzimidazolyl) benzene (TPBi) ETL, the recombination zone is close to the interface of the QD/ETL and moved to the interface of the QD/HTL with the increase in the driving voltage. Our results can also clarify the light emission mechanism in QLEDs. In devices with ZnMgO ETL, the emission is dominated by the direct charge recombination, whereas in devices with TPBi ETL, the emission is contributed by both FRET and direct charge recombination. Our studies suggest that fluorescent probe can be a powerful tool for investigating the exciton recombination zone, light emission mechanism, and other fundamental processes in QLEDs.
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